Diethyl adduct with iodine

At present the most complete study of the sulfides as bases is that of Tamres et al. (341,343) on the cyclic compounds. In a very recent paper on the chai transfer interaction of these compounds with iodine (341) they arrive at an order which is supported by hydrogenbonding results communicated to them by Schleyer and a reexamination of their original report on the BFj adducts (343). This leads to the following ranking 5-membered ring (tetrahydrothiophene) > diethyl sulfide > 6 > 4 > 3 which stands in contrast to the cyclic ethers 4 > 5 > 6 > 3. Partial support for the sulfide order is found in the results of McCullough and Zimmerman (240) who find the order... 

The Si—C bond in 1-organylsilatranes is easily cleaved by bromine or iodine chloride even at — 50 °C (equation 106)329. This route is observed in CH2CI2 or CHCI3 as a solvent. By using diethyl ether-bromine, THF-bromine or dioxane-bromine adducts, a mixture of 1-halo- and 1-haloalkoxysilatranes is formed. For example, the reaction of 1-phenylsilatrane (21) with dioxane-bromine results in 1-bromosilatrane (50) and l-[2 -(2"-bromoethoxy)ethoxy]silatrane (73) in 39% and 12% yield, respectively (equation 107)329. 

The original set of E and C parameters was determined mainly with the help of enthalpies of adduct formation of iodine and phenol as acceptors with alkylamines as donors. Subsequently, the best set of E and C parameters has been obtained by computer optimization of a large data base of enthalpies and four arbitrarily fixed reference values [71, 215] E = C = for iodine, E = 1.32 for A, A -dimethylacetamide, and Cb = 7.40 for diethyl sulfane. Table 2-6 gives a selection of E and C parameters for Lewis acids and bases commonly used as solvents. 

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